Synthesis of Imidazo[5,1-a]isoquinoline and Its 3-Substituted Analogues Including the Fluorescent 3-(1-Isoquinolinyl)imidazo[5,1-a]isoquinoline

Compounds having imidazo[5,1-a]isoquinoline nucleus have been synthesised. Selenium dioxide oxidation of a mixture of various aldehydes and 1-isoquinolinemethylamine yielded the respective 3-substituted imidazo[5,1-a]isoquinolines in good yields. When 1-isoquinolinemethylamine was employed without any aldehyde, 3-(1-isoquinolinyl)imidazo[5,1-a]isoquinoline (IQ-1) was isolated. This IQ-1 is fluorescent and all the compounds were thoroughly characterized. Molecular structures of IQ-1 and 3-(2-hydroxyphenyl)imidazo[5,1-a]isoquinoline (IQ-4) have been confirmed by single crystal X-ray diffraction technique.